Image coding method of encoding components of a motion vector and arranging the encoded components in a bitstream

ABSTRACT

An image coding method includes coding a motion vector difference indicating a difference between the motion vector and a predicted motion vector, wherein the coding includes: coding a first portion that is a part of a first component which is one of a horizontal component and a vertical component of the motion vector difference; coding a second portion that is a part of a second component which is different from the first component and is the other one of the horizontal component and the vertical component; coding a third portion that is a part of the first component and is different from the first portion; coding a fourth portion that is a part of the second component and is different from the second portion; and generating a code string which includes the first portion, the second portion, the third portion, and the fourth portion in the stated order.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 13/529,384,filed Jun. 21, 2012, which claims the benefit of U.S. Provisional PatentApplication No. 61/500,805 filed on Jun. 24, 2011. The entiredisclosures of the above-identified applications, including thespecification, drawings and claims, are incorporated herein by referencein their entirety.

TECHNICAL FIELD

One or more exemplary embodiments disclosed herein relate generally toimage coding methods for coding images using motion vectors.

BACKGROUND ART

Examples of techniques regarding an image coding method for codingimages using motion vectors include techniques described in Non PatentLiteratures (NPLs) 1 and 2.

CITATION LIST Non Patent Literature

-   [NPL 1] ITU-T Recommendation H.264 “Advanced video coding for    generic audio visual services”, March, 2010-   [NPL 2] JCT-VC “WD3: Working Draft 3 of High-Efficiency Video    Coding”, JCTVC-E603, March 2011

SUMMARY OF INVENTION Technical Problem

Inefficient coding of an image causes delay in processing and alsoaffects decoding of the image.

In view of this, one non-limiting and exemplary embodiment provides animage coding method for efficiently coding information constituting animage.

Solution to Problem

Additional benefits and advantages of the disclosed embodiments will beapparent from the Specification and Drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the Specification and Drawings which need not all beprovided in order to obtain one or more of the same.

In one general aspect, the techniques disclosed here feature an imagecoding method for coding an image using a motion vector, the methodincluding coding a motion vector difference indicating a differencebetween the motion vector and a predicted motion vector which is apredicted value of the motion vector, wherein the coding includes:coding a first portion that is a part of a first component which is oneof a horizontal component and a vertical component of the motion vectordifference; coding a second portion that is a part of a second componentwhich is different from the first component and is the other one of thehorizontal component and the vertical component; coding a third portionthat is a part of the first component and is different from the firstportion; coding a fourth portion that is a part of the second componentand is different from the second portion; and generating a code stringwhich includes the first portion, the second portion, the third portion,and the fourth portion in an order of the first portion, the secondportion, the third portion, and the fourth portion.

These general and specific aspects may be implemented using anapparatus, a system, an integrated circuit, a computer program, or anon-transitory computer-readable recording medium such as a CD-ROM, orany combination of apparatuses, systems, integrated circuits, computerprograms, or recording media.

Advantageous Effects of Invention

Information constituting an image is efficiently coded according toexemplary embodiments disclosed herein.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features will become apparent from thefollowing description thereof taken in conjunction with the accompanyingDrawings. In the Drawings:

FIG. 1 is a block diagram showing an example of a configuration of aconventional motion vector difference decoding method;

FIG. 2 is a flowchart showing a flow of operation of the conventionalmotion vector difference decoding method;

FIG. 3 is a flowchart showing context adaptive binary arithmeticdecoding processing of the conventional arithmetic decoding method;

FIG. 4 is a flowchart showing bypass arithmetic decoding processing ofthe conventional arithmetic decoding method;

FIG. 5 is a flowchart showing normalization processing of theconventional arithmetic decoding method;

FIG. 6 is a schematic diagram showing examples of binary strings ofmotion vector differences;

FIG. 7 is a block diagram showing a functional configuration of adecoding apparatus according to Embodiment 1;

FIG. 8 is a flowchart showing processing operation of the decodingapparatus according to Embodiment 1;

FIG. 9 is a diagram for describing examples of processing executed inEmbodiment 1;

FIG. 10 is a block diagram showing an example of a configuration of animage decoding device according to Embodiment 1;

FIG. 11A is a table showing examples of binary code strings according toa modification of Embodiment 1;

FIG. 11B is a flowchart showing processing operation of a decodingapparatus according to the modification of Embodiment 1;

FIG. 12 is a flowchart showing processing operation of a codingapparatus according to Embodiment 2;

FIG. 13 is a syntax table showing an example of a data structure;

FIG. 14 is a block diagram showing an example of a configuration of animage coding apparatus according to Embodiment 2;

FIG. 15A is a block diagram showing an example of a configuration of animage coding apparatus according to Embodiment 3;

FIG. 15B is a flowchart showing processing operation of the image codingapparatus according to Embodiment 3;

FIG. 16A is a block diagram showing an example of a configuration of animage decoding apparatus according to Embodiment 3;

FIG. 16B is a flowchart showing processing operation of the imagedecoding apparatus according to Embodiment 3;

FIG. 17 is a syntax table showing an example of a data structure of acode string corresponding to a motion vector difference;

FIG. 18 shows an overall configuration of a content providing system forimplementing content distribution services;

FIG. 19 shows an overall configuration of a digital broadcasting system;

FIG. 20 shows a block diagram illustrating an example of a configurationof a television;

FIG. 21 shows a block diagram illustrating an example of a configurationof an information reproducing/recording unit that reads and writesinformation from and on a recording medium that is an optical disk;

FIG. 22 shows an example of a configuration of a recording medium thatis an optical disk;

FIG. 23A shows an example of a cellular phone;

FIG. 23B is a block diagram showing an example of a configuration of acellular phone;

FIG. 24 illustrates a structure of multiplexed data;

FIG. 25 schematically shows how each stream is multiplexed inmultiplexed data;

FIG. 26 shows how a video stream is stored in a stream of PES packets inmore detail;

FIG. 27 shows a structure of TS packets and source packets in themultiplexed data;

FIG. 28 shows a data structure of a PMT;

FIG. 29 shows an internal structure of multiplexed data information;

FIG. 30 shows an internal structure of stream attribute information;

FIG. 31 shows steps for identifying video data;

FIG. 32 shows an example of a configuration of an integrated circuit forimplementing the moving picture coding method and the moving picturedecoding method according to each of embodiments;

FIG. 33 shows a configuration for switching between driving frequencies;

FIG. 34 shows steps for identifying video data and switching betweendriving frequencies;

FIG. 35 shows an example of a look-up table in which video datastandards are associated with driving frequencies;

FIG. 36A is a diagram showing an example of a configuration for sharinga module of a signal processing unit; and

FIG. 36B is a diagram showing another example of a configuration forsharing a module of the signal processing unit.

DESCRIPTION OF EMBODIMENTS Underlying Knowledge Forming Basis of thePresent Disclosure

The number of applications for, for example, video-on-demand typeservices which include video conference via the Internet, digital videobroadcasting, and streaming of video content is continuously increasing,and these applications are dependent on transmission of videoinformation. When video data is transmitted or recorded, a considerableamount of data is transmitted through a conventional transmissionchannel having a limited band width, or is stored in a conventionalstorage medium having a limited data capacity. It is necessary tocompress or reduce the amount of digital data, in order to transmitvideo information via a conventional transmission channel and storevideo information in a conventional storage medium.

In view of this, a plurality of video coding standards have beendeveloped to compress video data. Examples of such video codingstandards include the ITU-T standard typified by H.26x, and the ISO/IECstandard typified by MPEG-x. The latest and most advanced video codingstandard at present is a standard typified by H.264/MPEG-4 AVC (seeNon-Patent Literature (NPL) 1).

A coding approach which is the basis of most of these standards is basedon prediction coding which includes main steps shown by (a) to (d)below. Step (a): Divide video frames into pixel blocks, to perform datacompression on each video frame at a block level. Step (b): Identifytemporal and spatial redundancy by predicting individual blocks fromvideo data previously coded. Step (c): Eliminate the identifiedredundancy by subtracting predicted data from the video data. Step (d):Compress the remaining data (residual block) by performing Fouriertransform, quantization, and entropy coding.

In the above step (a), prediction modes used to predict macroblocks aredifferent for current video coding standards. Most of the video codingstandards use motion detection and motion compensation, in order topredict video data from a frame coded and decoded previously(inter-frame prediction). Alternatively, block data may be extrapolatedfrom an adjacent block in the same frame (intra-frame prediction).

For example, when a coding target picture is to be coded usinginter-frame prediction, an image coding apparatus uses, as a referencepicture, a coded picture that appears before or after the coding targetpicture in the display order. Then, the image coding apparatus performsmotion detection on the coding target picture relative to the referencepicture, thereby deriving a motion vector of each block. The imagecoding apparatus performs motion compensation using the motion vectorsderived in this way, to generate predicted image data. Then, the imagecoding apparatus codes a difference between the generated predictedimage data and image data of the coding target picture, thus reducingredundancy in the time direction.

Further, it is considered to use a predicted motion vector designationmode when a motion vector of a coding target block in a B-picture or aP-picture is coded (NPL 2). An image coding apparatus using thepredicted motion vector designation mode generates a plurality ofcandidates for a predicted motion vector, based on blocks for whichcoding has been performed and which are adjacent to a coding targetblock. Then, the image coding apparatus selects a predicted motionvector from among the plurality of generated candidates.

The image coding apparatus codes a motion vector of the coding targetblock using the selected predicted motion vector. Specifically, variablelength coding is performed on a motion vector difference between themotion vector of the coding target block and the selected predictedmotion vector.

Further, the image coding apparatus adds an index (also referred to as apredicted motion vector index) of the selected predicted motion vectorto a coded bit stream. Accordingly, at the time of decoding, the imagedecoding apparatus can select a predicted motion vector that is the sameas the predicted motion vector selected when coding is performed.

In addition, a more specific description of a method for performingvariable length decoding on a motion vector difference is given usingFIGS. 1 and 2. FIG. 1 is a block diagram showing an example of aconfiguration of a conventional method for performing variable lengthdecoding on a motion vector difference. FIG. 2 is a flowchart showing anexample of the flow of operation of the conventional method forperforming variable length decoding on a motion vector difference.

Motion vector difference values are binarized, and constitute binarystrings. Binary strings can be each separated into a flag indicating a(plus or minus) sign, a prefix portion corresponding to a portion of theabsolute value of a motion vector difference smaller than or equal to athreshold (TH) value, and a suffix portion corresponding to a portionthereof greater than the TH value (see FIG. 6).

A sign is + or −. For example, if a sign is +, a flag which indicatesthe sign is 0. If a sign is −, a flag which indicates the sign is 1.Further, the TH value is 8, for example. In this case, a prefix portioncorresponds to a portion constituting eight or less in a binarizedstring of the absolute value of a motion vector difference. A suffixportion corresponds to a portion which constitutes nine or more in abinarized string of the absolute value of a motion vector difference.

Arithmetic coding and decoding methods are different for the flagindicating a sign, the prefix portion, and the suffix portion.Arithmetic coding and decoding methods will be described below.

A motion vector difference variable length decoding unit A00 obtains abit stream BS which includes motion vector difference information, andinputs the obtained bit stream BS to a motion vector differencereconstruction control unit A01 and a motion vector difference 0determination unit A02. It should be noted that here, the motion vectordifference reconstruction control unit A01 takes in an X component(horizontal component) and a Y component (vertical component) of theobtained motion vector difference information in the stated order, andmanages whether a component of the motion vector difference informationon which decoding processing is being performed is an X component or a Ycomponent.

The motion vector difference 0 determination unit A02 decodes, from theobtained bit stream, a flag indicating whether the X component of themotion vector difference is 0 (step SB00). If the X component of themotion vector difference is not 0 (NO in step SB01), a motion vectordifference prefix portion decoding unit A03 decodes the prefix portionof the X component of the motion vector difference (step SB02). Next, ifthe X component of the motion vector difference includes the suffixportion (YES in step SB03), a motion vector difference suffix portiondecoding unit A04 decodes the suffix portion of the X component of themotion vector difference (SB04). If the X component does not include thesuffix portion (NO in SB03), suffix decoding processing is skipped.Next, a motion vector difference sign decoding unit A05 decodes the signof the X component of the motion vector difference, and a motion vectordifference reconstruction unit A06 reconstructs and sets the X componentof the motion vector difference (SB05).

On the other hand, if the X component of the motion vector difference is0 (YES in step SB01), the motion vector difference reconstruction unitA06 sets the X component of the motion vector difference to 0 (stepSB06). Here, the motion vector difference reconstruction control unitA01 switches a switch A07 to a side indicating an X component (aterminal on an upper side in FIG. 1), and outputs the X component of themotion vector difference.

Next, a Y component of the motion vector difference is decoded as withthe case of the X component. It should be noted that in the followingprocedure of the operation, step SB07 corresponds to step SB00, stepSB08 corresponds to step SB01, step SB09 corresponds to step SB02, stepSB10 corresponds to step SB03, step SB11 corresponds to step SB04, stepSB12 corresponds to step SB05, and step SB13 corresponds to step SB06.Accordingly, the operation in these steps is the same except that thecomponents are different, and thus a detailed description is omitted.

At the end of all the steps, the X component and the Y component of themotion vector difference are reconstructed.

Next is a description of variable length coding on a difference betweenpredicted image data and image data of a coding target picture and amotion vector difference between a predicted motion vector and a motionvector, and the like. In H.264, one of the variable length codingmethods is context adaptive binary arithmetic coding (CABAC). Thefollowing is a description of this CABAC using FIGS. 3, 4, and 5.

FIG. 3 shows the flow of conventional context adaptive binary arithmeticdecoding processing mentioned above. It should be noted that thisdrawing is extracted from NPL 1, and is as described in NPL 1, unless adescription is particularly given.

In arithmetic decoding processing, first, a context (ctxIdx) determinedbased on a signal type is input.

Next, a value qCodIRangeIdx derived from a parameter codIRange whichindicates the state in an arithmetic decoding apparatus at this point intime is calculated, and a pStateIdx value which is a state valuecorresponding to ctxIdx is obtained. Using the two values, codIRangeLPSis obtained by referring to a table (rangeTableLPS). It should be notedthat this codIRangeLPS indicates a value corresponding to the firstparameter codIRange indicating the state in the arithmetic decodingapparatus when LPS (indicating a symbol 0 or 1 whose probability ofoccurrence is the lower) has occurred.

Further, a value obtained by decrementing the current codIRange by theabove codIRangeLPS is put in codIRange (step SC01). Next, the calculatedcodIRange is compared with a second parameter codIOffset indicating thestate in the arithmetic decoding apparatus (step SC02).

If codIOffset is equal to or greater than the second parameter (YES inSC02), it is determined that the symbol of LPS has occurred. Then,binVal which is a decoded output value is set to a value different fromvaIMPS (a specific value (0 or 1) of MPS which indicates a symbol 0 or 1whose probability of occurrence is the higher), the different valuebeing 0 in the case of vaIMPS=1 and 1 in the case of vaIMPS=0. Further,the second parameter codIOffset indicating the state in the arithmeticdecoding apparatus is set to a value obtained as a result of decrementby codIRange. Since LPS has occurred, the first parameter codIRangeindicating the state in the arithmetic decoding apparatus is set to thevalue of codIRangeLPS calculated in step SC01 (step SC03).

It should be noted that here, if the above pStateIdx value which is astate value corresponding to ctxIdx is 0 (YES in step SC05), the casewhere the probability of LPS exceeds the probability of MPS isindicated. Thus, vaIMPS is switched (to 0 in the case of vaIMPS=1 and to1 in the case of vaIMPS=0) (step SC06). On the other hand, if thepStateIdx value is not 0 (NO in step SC05), the pStateIdx value isupdated based on a transition table transIdxLPS used when LPS occurs(step SC07).

If codIOffset is smaller (NO in SC02), it is determined that the symbolof MPS has occurred. Then, binVal which is a decoded output value is setto vaIMPS, and the pStateIdx value is updated based on a transitiontable transIdxMPS used when MPS occurs (step SC04).

At last, normalization processing (RenormD) is performed (step SC08),and arithmetic decoding ends.

As described above, in context adaptive binary arithmetic decodingprocessing, a plurality of symbol occurrence probabilities which are theprobabilities of occurrence of binary symbols are held in associationwith context indexes, and switched according to conditions (by referringto a value of an adjacent block, for example). Thus, it is necessary tokeep the order of processing.

FIG. 4 shows the flow of the above conventional arithmetic decodingprocessing for bypass processing. It should be noted that this drawingis extracted from NPL 1, and is as described in NPL 1, unless adescription is particularly given.

First, the second parameter codIOffset indicating the state in thearithmetic decoding device at this point in time is shifted to the left(doubled), and one bit is read from a bit stream. If the read bitindicates 1, 1 is added to the doubled second parameter codIOffset,whereas if the value indicates 0, the second parameter codIOffset is setto the as-is value (which has been doubled) (SD01).

Next, if codIOffset is greater than or equal to the first parametercodIRange indicating the state in the arithmetic decoding device (YES inSD02), binVal which is a decoded output value is set to “1”. Then,codIOffset is set to a value obtained as a result of decrement bycodIRange (step SD03). On the other hand, if codIOffset is smaller thanthe first parameter codIRange which indicates the state in thearithmetic decoding device (NO in SD02), binVal which is a decodedoutput value is set to “0” (step SD04).

FIG. 5 is a flowchart for describing in detail the normalizationprocessing (RenormD) shown by step SC08 in FIG. 3. This drawing isextracted from NPL 1, and is as described in NPL 1, unless a descriptionis particularly given.

If the first parameter codIRange indicating the state in the arithmeticdecoding apparatus becomes smaller than 0x100 (in hexadecimal: 256 (indecimal)) as a result of arithmetic decoding processing (YES in stepSE01), codIRange is shifted to the left (doubled), and the secondparameter codIOffset indicating the state in the arithmetic decodingdevice is shifted to the left (doubled). Then, one bit is read from abit stream. If the read bit indicates 1, 1 is added to the doubledsecond parameter codIOffset, whereas if the value indicates 0, thesecond parameter codIOffset is set to the as-is value (which has beendoubled) (SE02).

At the point in time when codIRange has eventually become 256 or greater(NO in step SE01), this processing ends.

Arithmetic decoding is performed on a motion vector difference byperforming the above processing shown in FIGS. 3, 4, and 5.

However, conventionally, when arithmetic coding is performed on a motionvector difference between a predicted motion vector and a motion vector,an X component and a Y component of the motion vector difference arecoded in order. Specifically, an X component of the motion vectordifference and a Y component of the motion vector difference are storedseparately in a coded stream. Thus, context adaptive binary arithmeticcoding and bypass coding are alternately executed on each of an Xcomponent and a Y component at the time of coding, and context adaptivebinary arithmetic decoding and bypass decoding are alternately executedon each of an X component and a Y component at the time of decoding,resulting in a problem that sufficient parallel processing is notallowed which is an advantage of bypass coding and decoding.

In view of this, an image coding method according to an exemplaryembodiment of the present disclosure is an image coding method forcoding an image using a motion vector, the method including coding amotion vector difference indicating a difference between the motionvector and a predicted motion vector which is a predicted value of themotion vector, wherein the coding includes: coding a first portion thatis a part of a first component which is one of a horizontal componentand a vertical component of the motion vector difference; coding asecond portion that is a part of a second component which is differentfrom the first component and is the other one of the horizontalcomponent and the vertical component; coding a third portion that is apart of the first component and is different from the first portion;coding a fourth portion that is a part of the second component and isdifferent from the second portion; and generating a code string whichincludes the first portion, the second portion, the third portion, andthe fourth portion in an order of the first portion, the second portion,the third portion, and the fourth portion.

Accordingly, a part of the horizontal component of the motion vectordifference and a part of the vertical component of the motion vectordifference are combined in the code string. For example, if a portionfor which bypass decoding is to be used and which is included in thehorizontal component and a portion for which bypass decoding is to beused and which is included in the vertical component are combined in acode string, the degree of parallelism of decoding processing may beincreased. In other words, the motion vector difference is efficientlycoded by combining a part of the horizontal component and a part of thevertical component.

For example, the coding the motion vector difference may include: codingthe third portion which includes a plus or minus sign of the firstcomponent, and coding the fourth portion which includes a plus or minussign of the second component; and generating the code string whichincludes the first portion, the second portion, the third portion, andthe fourth portion in the order of the first portion, the secondportion, the third portion, and the fourth portion.

Accordingly, the sign of the horizontal component and the sign of thevertical component are combined in the code string. Typically, bypassdecoding is used for decoding the signs. Therefore, the degree ofparallelism of decoding processing may be increased.

Further, for example, the coding the motion vector difference mayinclude: coding the first portion which includes a flag indicatingwhether the first component is 0, and coding the second portion whichincludes a flag indicating whether the second component is 0; andgenerating the code string which includes the first portion, the secondportion, the third portion, and the fourth portion in the order of thefirst portion, the second portion, the third portion, and the fourthportion.

Accordingly, the flag indicating whether the horizontal component is 0and the flag indicating whether the vertical component is 0 are combinedin the code string. Typically, context adaptive binary arithmeticdecoding is used for decoding the flags. A plurality of differentportions for which bypass decoding is to be used are combined in thecode string by combining the flags in the code string. Therefore, thedegree of parallelism of decoding processing may be increased.

Further, for example, the coding the motion vector difference mayinclude: coding the third portion which includes a difference between athreshold value and an absolute value of the first component when theabsolute value of the first component is greater than the thresholdvalue; coding the fourth portion which includes a difference between thethreshold value and an absolute value of the second component when theabsolute value of the second component is greater than the thresholdvalue; and generating the code string which includes the first portion,the second portion, the third portion, and the fourth portion in theorder of the first portion, the second portion, the third portion, andthe fourth portion.

Accordingly, the difference between the threshold value and the absolutevalue of the horizontal component and the difference between thethreshold value and the absolute value of the vertical component arecombined in the code string. Typically, bypass decoding is used fordecoding these differences. Therefore, the degree of parallelism ofdecoding processing may be increased.

Further, for example, the coding the motion vector difference mayinclude: coding the first portion and the second portion by performingcontext adaptive binary arithmetic coding which is arithmetic coding inwhich a variable probability updated based on coded data is used; andgenerating the code string which includes the first portion, the secondportion, the third portion, and the fourth portion in the order of thefirst portion, the second portion, the third portion, and the fourthportion.

Accordingly, a plurality of portions for which context adaptive binaryarithmetic decoding is to be used are combined in the code string. Inthis case, a plurality of different portions for which bypass decodingis to be used are combined in the code string. Therefore, the degree ofparallelism of decoding processing may be increased.

Further, for example, the coding the motion vector difference mayinclude: coding the third portion and the fourth portion by performingbypass coding which is arithmetic coding in which a predetermined fixedprobability is used; and generating the code string which includes thefirst portion, the second portion, the third portion, and the fourthportion in the order of the first portion, the second portion, the thirdportion, and the fourth portion.

Accordingly, a plurality of portions for which bypass decoding is to beused are combined in the code string. Therefore, the degree ofparallelism of decoding processing may be increased.

Further, for example, in the coding the motion vector difference, thethird portion and the fourth portion may be coded in parallel.

Accordingly, a part of the horizontal component and a part of thevertical component are coded in parallel. Therefore, the motion vectordifference is coded efficiently.

Further, for example, the coding the motion vector difference mayinclude: switching coding processing to first coding processingconforming to a first standard or to second coding processing conformingto a second standard, and generating a bit stream which includesidentification information indicating the first standard or the secondstandard to which a corresponding one of the first coding processing andthe second coding processing to which the coding processing has beenswitched conforms; and generating, when the coding processing isswitched to the first coding processing, the code string which includesthe first portion, the second portion, the third portion, and the fourthportion in the order of the first portion, the second portion, the thirdportion, and the fourth portion, and generating the bit stream whichincludes the code string and the identification information whichindicates the first standard.

Accordingly, an apparatus which is to perform decoding is notified ofwhether a part of the horizontal component of the motion vectordifference and a part of the vertical component of the motion vectordifference are combined in the code string. Therefore, decodingprocessing can be switched appropriately.

Further, an image decoding apparatus according to an exemplaryembodiment of the present disclosure may be an image decoding method fordecoding an image using a motion vector, the method including decoding amotion vector difference indicating a difference between the motionvector and a predicted motion vector which is a predicted value of themotion vector, wherein the decoding may include: obtaining a code stringwhich includes (i) a first portion that is a part of a first componentwhich is one of a horizontal component and a vertical component of themotion vector difference, (ii) a second portion that is a part of asecond component which is different from the first component and is theother one of the horizontal component and the vertical component, (iii)a third portion that is a part of the first component and is a differentfrom the first portion, and (iv) a fourth portion which is a part of thesecond component and is different from the second portion, in an orderof the first portion, the second portion, the third portion, and thefourth portion; and decoding the first portion included in the codestring, decoding the second portion included in the code string,decoding the third portion included in the code string, and decoding thefourth portion included in the code string.

Accordingly, the code string is obtained in which a part of thehorizontal component of the motion vector difference and a part of thevertical component of the motion vector difference are combined. Forexample, if a portion for which bypass decoding is to be used and whichis included in the horizontal component and a portion for which bypassdecoding is to be used and which is included in the vertical componentsare combined in the code string, the degree of parallelism of decodingprocessing may be increased. In other words, the motion vectordifference is efficiently decoded by using the code string in which apart of the horizontal component and a part of the vertical componentare combined.

For example, the decoding the motion vector difference may include:obtaining the code string which includes (i) the first portion, (ii) thesecond portion, (iii) the third portion which includes a plus or minussign of the first component, and (iv) the fourth portion which includesa plus or minus sign of the second component, in the order of the firstportion, the second portion, the third portion, and the fourth portion;and decoding the first portion included in the code string, decoding thesecond portion included in the code string, decoding the third portionincluded in the code string, and decoding the fourth portion included inthe code string.

Accordingly, the code string is obtained in which the sign of thehorizontal component and the sign of the vertical component arecombined. Typically, bypass decoding is used for decoding the signs.Therefore, the degree of parallelism of decoding processing may beincreased.

Further, for example, the decoding the motion vector difference mayinclude: obtaining the code string which includes (i) the first portionwhich includes a flag indicating whether the first component is 0, (ii)the second portion which includes a flag indicating whether the secondcomponent is 0, (iii) the third portion, and (iv) the fourth portion, inthe order of the first portion, the second portion, the third portion,and the fourth portion; and decoding the first portion included in thecode string, decoding the second portion included in the code string,decoding the third portion included in the code string, and decoding thefourth portion included in the code string.

Accordingly, the code string is obtained in which the flag indicatingwhether the horizontal component is 0 and the flag indicating whetherthe vertical component is 0 are combined. Typically, context adaptivebinary arithmetic decoding is used to decode these flags. A plurality ofdifferent portions for which bypass decoding is to be used are combinedin the code string by combining these flags in the code string.Therefore, the degree of parallelism of decoding processing may beincreased.

Further, for example, the decoding the motion vector difference mayinclude: obtaining the code string which includes (i) the first portion,(ii) the second portion, and (iii) the third portion which includes adifference between a threshold value and an absolute value of the firstcomponent when the absolute value of the first component is greater thanthe threshold value, and (iv) the fourth portion which includes adifference between the threshold value and an absolute value of thesecond component when the absolute value of the second component isgreater than the threshold value, in the order of the first portion, thesecond portion, the third portion, and the fourth portion; and decodingthe first portion included in the code string, decoding the secondportion included in the code string, decoding the third portion includedin the code string, and decoding the fourth portion included in the codestring.

Accordingly, the code string is obtained in which the difference betweenthe threshold value and the absolute value of the horizontal componentand the difference between the threshold value and the absolute value ofthe vertical component are combined. Typically, bypass decoding is usedfor decoding these differences. Therefore, the degree of parallelism ofdecoding processing may be increased.

Further, for example, the decoding the motion vector difference mayinclude: obtaining the code string which includes (i) the first portionto be decoded by performing context adaptive binary arithmetic decodingwhich is arithmetic decoding in which a variable probability updatedbased on decoded data is used, (ii) the second portion to be decoded byperforming the context adaptive binary arithmetic decoding, (iii) thethird portion, and (iv) the fourth portion, in the order of the firstportion, the second portion, the third portion, and the fourth portion;and decoding the first portion included in the code string by performingthe context adaptive binary arithmetic decoding, decoding the secondportion included in the code string by performing the context adaptivebinary arithmetic decoding, decoding the third portion included in thecode string, and decoding the fourth portion included in the codestring.

Accordingly, the code string is obtained in which a plurality ofportions for which context adaptive binary arithmetic decoding is to beused are combined. In this case, a plurality of different portions forwhich bypass decoding is to be used are combined in the code string.Therefore, the degree of parallelism of decoding processing may beincreased.

Further, for example, the decoding the motion vector difference mayinclude: obtaining the code string which includes (i) the first portion,(ii) the second portion, (iii) the third portion to be decoded byperforming bypass decoding which is arithmetic decoding in which apredetermined fixed probability is used, and (iv) the fourth portion tobe decoded by performing the bypass decoding, in the order of the firstportion, the second portion, the third portion, and the fourth portion;and decoding the first portion included in the code string, decoding thesecond portion included in the code string, decoding the third portionincluded in the code string by performing the bypass decoding, anddecoding the fourth portion included in the code string by performingthe bypass decoding.

Accordingly, the code string is obtained in which a plurality ofportions for which bypass decoding is to be used are combined.Therefore, the degree of parallelism of decoding processing may beincreased.

Further, for example, in the decoding the motion vector difference, thethird portion and the fourth portion may be decoded in parallel.

Accordingly, a part of the horizontal component and a part of thevertical component are decoded in parallel. Therefore, the motion vectordifference is decoded efficiently.

Further, for example, the decoding the motion vector difference mayinclude: obtaining a bit stream which includes identificationinformation indicating a first standard or a second standard, and basedon the identification information, switching decoding processing tofirst decoding processing conforming to the first standard or to seconddecoding processing conforming to the second standard; and when thedecoding processing is switched to the first decoding processing,obtaining the code string from the bit stream, decoding the firstportion included in the code string, decoding the second portionincluded in the code string, decoding the third portion included in thecode string, and decoding the fourth portion included in the codestring.

Accordingly, decoding processing is appropriately switched according towhether a part of the horizontal component of the motion vectordifference and a part of the vertical component of the motion vectordifference are combined in the code string.

Furthermore, these general and specific embodiments may be implementedusing an apparatus, a system, an integrated circuit, a computer program,or a non-transitory computer-readable recording medium such as a CD-ROM,or any combination of apparatuses, systems, integrated circuits,computer programs, or recording media.

The following is a detailed description of an image coding method and animage decoding method according to exemplary embodiments of the presentdisclosure using drawings. Each of the exemplary embodiments describedbelow shows a general or specific example. The numerical values, shapes,materials, constituent elements, the arrangement and connection of theconstituent elements, steps, the processing order of the steps, and thelike shown in the following exemplary embodiments are mere examples, andtherefore do not limit the inventive concept, the scope of which isdefined in the appended Claims and their equivalents. Therefore, amongthe constituent elements in the following exemplary embodiments,constituent elements not recited in any of the independent claimsdefining the most generic part of the inventive concept are described asarbitrary constituent elements.

Embodiment 1

FIG. 7 is a block diagram showing the functional configuration of amotion vector difference decoding unit 100 according to Embodiment 1.

The motion vector difference decoding unit 100 according to the presentembodiment includes a prefix portion decoding unit 110, a suffix portiondecoding unit 120, a motion vector difference reconstruction controlunit 101, and a motion vector difference reconstruction unit 106. Amongthese, the prefix portion decoding unit 110 is constituted by a motionvector difference 0 determination unit 102 and a motion vectordifference prefix portion decoding unit 103. Also, the suffix portiondecoding unit 120 is constituted by a motion vector difference suffixportion decoding unit 104 and a motion vector difference sign decodingunit 105. The motion vector difference decoding unit 100 reconstructs,from a bit stream BS, information on an X component MVDX and a Ycomponent MVDY of a motion vector difference.

The operation of the motion vector difference decoding unit 100 in thepresent embodiment is described in detail using FIG. 8. FIG. 8 is aflowchart showing an example of a flow of operation of the motion vectordifference decoding unit 100 of the present embodiment.

First, the motion vector difference 0 determination unit 102 decodes,from an obtained bit stream, a flag which indicates whether an Xcomponent of a motion vector difference is 0 (S200). Here, if the Xcomponent of the motion vector difference is not 0 (NO in S201), themotion vector difference prefix portion decoding unit 103 decodes aprefix portion of the X component of the motion vector difference(S202). On the other hand, if the X component of the motion vectordifference is 0 (YES in S201), the X component of the motion vectordifference is set to 0 (S203).

Next, returning back to the processing from the loop, the motion vectordifference 0 determination unit 102 decodes a flag which indicateswhether the Y component of the motion vector difference is 0 (S204). Ifthe Y component of the motion vector difference is not 0 here (NO inS205), the motion vector difference prefix portion decoding unit 103decodes a prefix portion of the Y component of the motion vectordifference (S206). On the other hand, if the Y component of the motionvector difference is 0 (YES in S205), the Y component of the motionvector difference is set to 0 (S207). It should be noted that theprocessing up to this step is the operation performed by the motionvector difference prefix portion decoding unit 103 (S280).

Next, if it is determined, based on decoded information on the Xcomponent of the motion vector difference, that the X component is not 0(NO in S208), and includes a suffix portion (YES in S209), the motionvector difference suffix portion decoding unit 104 decodes, from the bitstream, the suffix portion of the X component of the motion vectordifference (S210). On the other hand, if the suffix portion is notincluded (NO in S209), decoding processing on the suffix portion isskipped. It should be noted that here, regarding whether a suffixportion is included, the prefix portion and the suffix portion areseparated in a binary code string as shown in FIG. 6, for example, andthus it is determined that a suffix portion is included if all thedigits in a prefix portion are 1.

Next, the motion vector difference sign decoding unit 105 decodes, fromthe bit stream, the sign of the motion vector difference, and the motionvector difference reconstruction unit 106 reconstructs the X componentof the motion vector difference (S211). On the other hand, if the Xcomponent is 0 (YES in S208), the X component of the motion vectordifference has already been successfully reconstructed, and thusdecoding processing on the suffix portion of the X component is skipped.

Next, if it is determined, based on decoded information on the Ycomponent of the motion vector difference, that the Y component is not 0(NO in S212), and includes a suffix portion (YES in S213), the motionvector difference suffix portion decoding unit 104 decodes, from the bitstream, the suffix portion of the Y component of the motion vectordifference (S214). It should be noted that if the suffix portion is notincluded (NO in S213), decoding processing on the suffix portion isskipped. Here, whether a suffix portion is included may be determined inthe same manner as the case of the X component. Next, the motion vectordifference sign decoding unit 105 decodes, from the bit stream, the signof the Y component of the motion vector difference, and the motionvector difference reconstruction unit 106 reconstructs the Y componentof the motion vector difference (S215). On the other hand, if the Ycomponent is 0 (YES in S212), the Y component of the motion vectordifference has already been successfully reconstructed, and thusdecoding processing on the suffix portion of the Y component is skipped.

It should be noted that for the prefix portion, information of a motionvector difference has a high tendency (there tends to be many zerovectors), and thus coding efficiency increases by performing contextadaptive binary arithmetic coding described above. Accordingly, contextadaptive binary arithmetic decoding processing (FIG. 3) is executed atthe time of decoding.

On the other hand, the suffix portion corresponds to lower bits of alarge motion vector difference. Thus, the range of possible values islarge (for example, 9 to 1024), and frequencies at which the same binarycode string symbol occurs tend to be low. Accordingly, the amount ofprocessing is reduced by performing bypass coding, assuming that theprobability of symbol occurrence is 50%. Specifically, bypass decoding(FIG. 4) is executed when a suffix portion is decoded. It should benoted that if the sign of a motion vector difference is included, bypasscoding is also performed on the sign, and thus bypass decoding isexecuted.

Here, an example of operation of decoding processing shown in FIG. 8 isdescribed using FIG. 9.

FIG. 9 is a drawing for describing examples of steps of processingexecuted in Embodiment 1. In FIG. 9, (a) shows an example in the casewhere processing executed in Embodiment 1 is performed in parallel withone process. Processing is performed in the order of decoding on aprefix portion of an X component of a motion vector difference(MVDX_PREFIX), decoding on a prefix portion of a Y component thereof(MVDY_PREFIX), decoding on a suffix portion of the X component(MVDX_SUFFIX), decoding on the sign of the X component (MVDX_SIGN),decoding on the suffix portion of the Y component (MVDY_SUFFIX), anddecoding on the sign of the Y component (MVDY_SIGN).

However, high-speed processing is required due to an increase inutilized image resolution and an expansion of high-speed real timecommunication, and thus parallelized processing is implemented. However,since context adaptive binary arithmetic coding processing is performedon a prefix portion, it is necessary to successively perform processingof reading and updating the probability of symbol occurrence. Thus,processing on a prefix portion cannot be parallelized. However, a bypassprocessing portion can be parallelized bitwise, as shown in (b) in FIG.9.

In contrast, (c) and (d) in FIG. 9 are examples of parallelization ofprocessing executed in the conventional configuration. In FIG. 9, (c)corresponds to (a) in FIG. 9, and (d) in FIG. 9 corresponds to (b) inFIG. 9. Similarly, processing is successively performed on a prefixportion, namely, a context adaptive binary arithmetic decodingprocessing portion, and processing on a suffix portion, namely, bypassprocessing portion can be parallelized. However, since an X componentand a Y component are alternately arranged, portions on which processingcan be performed in parallel are not consecutively arranged. Thus, asufficient increase in speed cannot be achieved ((d) in FIG. 9).Further, processing is often switched between context adaptive binaryarithmetic decoding and bypass decoding, which results in a great loadon and a considerable delay in processing.

It should be noted that the arithmetic decoding unit 100 according toEmbodiment 1 is included in the image decoding apparatus which decodescoded image data on which compression coding has been performed. FIG. 10is a block diagram showing an example of a configuration of an imagedecoding apparatus 400 according to Embodiment 1.

The image decoding apparatus 400 decodes coded image data on whichcompression coding has been performed. For example, coded image data isinput, on a block-by-block basis, to the image decoding apparatus 400 assignals to be decoded. The image decoding apparatus 400 reconstructsimage data by performing variable length decoding, inverse quantization,and inverse transform on the input decoding target signals.

As shown in FIG. 10, the image decoding apparatus 400 includes anentropy decoding unit 410, an inverse quantization and inverse transformunit 420, an adder 425, a deblocking filter 430, a memory 440, an intraprediction unit 450, a motion compensation unit 460, and an intra/interchange switch 470.

The entropy decoding unit 410 performs variable length decoding on aninput signal (input stream), to reconstruct a quantization coefficient.It should be noted that here, an input signal (input stream) is a signalto be decoded, and corresponds to coded image data for each block.Further, the entropy decoding unit 410 obtains motion data from theinput signal, and outputs the obtained motion data to the motioncompensation unit 460.

The inverse quantization and inverse transform unit 420 performs inversequantization on the quantization coefficient reconstructed by theentropy decoding unit 410, to reconstruct a transform coefficient. Then,the inverse quantization and inverse transform unit 420 performs inversetransform on the reconstructed transform coefficient, to reconstruct aprediction error.

The adder 425 adds the reconstructed prediction error to a predictedsignal, to generate a decoded image.

The deblocking filter 430 performs deblocking filter processing on thegenerated decoded image. The decoded image on which deblocking filterprocessing has been performed is output as a decoded signal.

The memory 440 is a memory for storing reference images used for motioncompensation. Specifically, the memory 440 stores decoded images onwhich deblocking filter processing has been performed.

The intra prediction unit 450 performs intra prediction, to generate apredicted signal (intra-predicted signal). Specifically, the intraprediction unit 450 performs intra prediction by referring to an imagearound a block to be decoded (input signal) in the decoded imagegenerated by the adder 425, to generate an intra-predicted signal.

The motion compensation unit 460 performs motion compensation, based onmotion data output from the entropy decoding unit 410, to generate apredicted signal (inter-predicted signal).

The intra/inter change switch 470 selects either one of theintra-predicted signal and the inter-predicted signal, and outputs theselected signal to the adder 425 as a predicted signal.

Using the above configuration, the image decoding apparatus 400according to Embodiment 1 decodes coded image data on which compressioncoding has been performed.

It should be noted that in the image decoding apparatus 400, the entropydecoding unit 410 includes the motion vector difference decoding unit100 according to Embodiment 1.

As described above, the image decoding apparatus and the image decodingmethod according to Embodiment 1 enable high-speed motion vectordifference decoding.

Specifically, as described in Embodiment 1, an X component and a Ycomponent of a motion vector difference value are integrated, and amotion vector difference value is separated into a portion on whichcontext adaptive binary arithmetic decoding is to be performed and aportion on which bypass processing is to be performed. Consequently, itis possible to expand a portion on which parallel operation can beperformed. Thus, parallel processing, or in other words, high-speeddecoding can be performed.

It should be noted that although the above describes decoding processingon a suffix portion and sign decoding processing, which are performed onan X component and a Y component separately, the inventive concept isnot limited to this. For example, after suffix portion decodingprocessing on an X component, suffix portion decoding processing on a Ycomponent, sign decoding processing on an X component, and then signdecoding processing on a Y component may be performed. Even with thisconfiguration, portions on which bypass processing is performed are insuccession, and thus advantageous effects can be expected to beobtained. Also, with respect to a prefix portion, information indicatingwhether an X component is 0, and information indicating whether a Ycomponent is 0 may be decoded in succession. The same restrictions on aportion on which context arithmetic decoding processing is performed(processing needs to be successively performed) are applied to eithercase.

It should be noted that a binary string shown in FIG. 6 and the lengthof a portion on which context adaptive binary arithmetic decoding isperformed are examples, and do not necessarily need to be the same as inthe above description. For example, decoding may be performed assumingthat a motion vector difference whose absolute value is 0, 1, or 2 is aprefix portion, whereas a motion vector difference whose absolute valueis greater than or equal to 3 is a suffix portion (as a matter ofcourse, the coding apparatus which generates this bit stream is assumedto have also performed the same processing). By determining a binarystring in this way, the degree of parallelism can be increased, anddecoding processing can be performed at a still higher speed.

Modification of Embodiment 1

It should be noted that in Embodiment 1, a motion vector difference isseparated into a prefix portion corresponding to a portion on whichcontext adaptive binary arithmetic decoding processing is performed anda suffix portion corresponding to a portion on which bypass decodingprocessing is performed, irrespective of an X component and a Ycomponent. This achieves high-speed processing. While achieving thispoint, it is possible to consider a modification as will be describedbelow.

The modification of Embodiment 1 is now described in detail using FIGS.11A and 11B. FIG. 11A is a flag correspondence table showing whether Xcomponents and Y components of motion vector differences are 0 in themodification of Embodiment 1. FIG. 11B is a flowchart showing an exampleof the flow of processing in the modification of Embodiment 1.

Embodiment 1 describes different flags indicating whether an X componentof a motion vector difference is 0 and whether a Y component of a motionvector difference is 0. However, an X component and a Y component of amotion vector difference are combined to perform decoding in Embodiment1, and thus coding efficiency can be further improved by combining theflags.

For example, as shown in FIG. 11A, codes (MVDXY_EXIST) are assigned tocombinations showing whether an X component is 0 (MVDX_EXIST) andwhether a Y component is 0 (MVDY_EXIST).

“0” is assigned if both of an X component and a Y component are 0, “111”is assigned if neither an X component nor a Y component is 0, “110” isassigned if an X component is 0, whereas a Y component is not 0, and“10” is assigned if a Y component is 0, whereas an X component is not 0.

As described above, it is considered to designate, using an index, amethod of performing derivation from neighboring vectors, as a method ofderiving a motion vector difference. Accordingly, a probability that acomponent of a motion vector difference is “0” is even higher thanconventional image coding. If both of an X component and a Y componentare “0”, a binary string signal can be expressed using 1 bit in thepresent modification, although conventionally 2 bits are necessary. Theflow of processing performed by the motion vector difference decodingunit 100 in the present modification is as shown in FIG. 11B.

In step S501, a code string which indicates whether an X component and aY component of a motion vector difference are 0 is obtained (S501).Here, for example, the correspondence table in FIG. 11A is applied to aresult showing whether an X component and a Y component are 0. It shouldbe noted that FIG. 11B is the same as FIG. 8 except for that steps S200and S204 in FIG. 8 are replaced with step S501, and thus a descriptionof the following steps is omitted.

It should be noted that the correspondence table shown in FIG. 11A is anexample. In the case of this example, binary strings are determined,assuming that a possibility of an X component of a motion vectordifference being 0 is low since generally many images horizontally move.For example, a motion vector difference coding unit may switch suchcorrespondence tables from one to another according to the codeoccurrence frequency, and may record an index indicating whichcorrespondence table is used for coding in a bit stream. Thereafter, themotion vector difference decoding unit 100 may obtain the correspondencetable in FIG. 11A by decoding the index.

This modification enables coding efficiency to be improved whileachieving high-speed processing.

Embodiment 2

The outline of an arithmetic coding method in the present embodiment isnow described. The arithmetic coding method in the present embodimenthas a feature of dividing a motion vector difference into a prefixportion corresponding to a portion on which context adaptive binaryarithmetic coding is performed and a suffix portion corresponding to aportion on which bypass processing coding is performed, rather thandividing a motion vector difference into an X component and a Ycomponent. This achieves parallelization of processing and high-speedcoding.

The above is a description of the outline of the arithmetic codingmethod in the present embodiment. The same method as the conventionalarithmetic coding method may be used, unless particularly described.

Next is a description of the flow of processing performed by the motionvector difference coding unit which carries out the motion vectordifference coding method in the present embodiment.

FIG. 12 is a flowchart showing the flow of processing performed by amotion vector difference coding unit according to Embodiment 2.

First, the motion vector difference coding unit obtains information onan X component and a Y component of a motion vector difference to becoded, and determines whether the X component of the motion vectordifference is 0 (S601). If the X component of the motion vectordifference is not 0 (NO in S601), coding processing is performed on aprefix portion of the X component of the motion vector difference(S602). It should be noted that in the coding processing on the prefixportion here, a binary string shown in FIG. 6 is coded using the contextadaptive binary arithmetic coding method described below. The contextadaptive binary arithmetic coding forms a pair with the arithmeticdecoding method in FIG. 3, and is a kind of arithmetic coding in whichcontexts are switched from one to another based on conditions, theprobability of symbol occurrence is obtained, and the probability valuethereof is updated using the coded symbol (see NPL 1). It should benoted that in the following, the context adaptive binary arithmeticcoding method is applied for coding a prefix portion, if not writtenclearly.

Next, if the X component of the motion vector difference is 0 (YES inS601), a flag is coded which indicates that the X component of themotion vector difference is 0 (S603). Next, it is determined whether theY component of the motion vector difference is 0 (S604). If the Ycomponent of the motion vector difference is not 0 (NO in S604), codingprocessing is performed on the prefix portion of the Y component of themotion vector difference (in the same manner as that for the Xcomponent, S605). On the other hand, if the Y component of the motionvector difference is 0, a flag is coded which indicates that the Ycomponent of the motion vector difference is 0 (S606).

Next, it is determined whether the X component of the motion vectordifference is greater than or equal to a TH value, or in other words, asuffix is included (S607). For example, if the binary string table inFIG. 6 is used, determination is made assuming that TH=9. It should benoted that in the present embodiment, a boundary between a prefix(context adaptive binary arithmetic coding) portion and a suffix (bypassprocessing coding) portion may be determined, irrespective of thisbinary string table.

If the X component includes a suffix portion here (YES in S607), thesuffix portion of the X component of the motion vector difference iscoded (S608). It should be noted that arithmetic coding bypassprocessing is performed for coding a suffix portion. Specifically, it isa method used to reduce calculation by fixing the probability to 50%,and forms a pair with the bypass decoding method shown in FIG. 4 (seeNPL 1). In the following, bypass coding is used for coding a suffixportion, if not clearly written. Next, the sign of the X component ofthe motion vector difference is coded. It should be noted that bypasscoding is also performed with respect to this processing (S610). Itshould be noted that the sign of the X component is coded also in thecase where a suffix portion is not included (NO in S607), and the Xcomponent is not 0 (NO in S609). After the end of suffix codingprocessing on the X component (S610 and YES in S609), suffix codingprocessing is performed on the Y component.

Next, it is determined whether the Y component of the motion vectordifference is greater than or equal to the TH value, or in other words,a suffix is included (S611). Since it is determined in the same manneras that for the X component, a detailed description is omitted.

If the Y component includes a suffix portion here (YES in S611), thesuffix portion of the Y component of the motion vector difference iscoded (S612). It should be noted that arithmetic coding bypassprocessing is performed for coding a suffix portion. Next, the sign ofthe Y component of the motion vector difference is coded. It should benoted that bypass coding is also performed with respect to thisprocessing (S614). It should be noted that the sign of the Y componentis also coded if the suffix portion is not included (NO in S611), andthe Y component is not 0 (NO in S613). This completes suffix codingprocessing on the Y component, and coding processing on the X componentand the Y component of the motion vector difference ends.

It should be noted that even using the method for coding a motion vectordifference, processing can be parallelized as in (b) in FIG. 9 describedin Embodiment 1, and thus a high-speed coding apparatus can be obtained.It should be noted that as a coding method for the modification ofEmbodiment 1, S601 and S604 in the processing flow in FIG. 12 areperformed first. Then, instead of S603 and S606, a binary string iscoded which indicates whether each of an X component and a Y componentin a combination is 0, based on the correspondence table of FIG. 11A. Itshould be noted that prefix coding, namely, the context adaptive binaryarithmetic coding method is also performed for coding in this case. Thisachieves a high-speed coding apparatus, while improving codingefficiency.

It should be noted that FIG. 13 is a schematic diagram for describingsyntax which shows an example of a data structure of this configuration.It should be noted that this syntax table is quoted from NPL 2, and isan example of a data structure in which the portions denoted by 701,702, and 703 are generated using the method for coding (decoding) amotion vector difference in Embodiment 2 (and Embodiment 1).

As shown by 701 to 703, mvd_I? which indicates a motion vectordifference is represented as a parameter which indicates both of an xcomponent and a y component. It should be noted that “?” in mvd_I?corresponds to a reference index, and is specifically c, 0, or 1 (seeNPL 2 for details).

A motion vector difference is conventionally represented as mvd_I? [x0][y0] [0] and mvd_I? [x0] [y0] [1]. Here, the last element [0] indicatesan X component, and the last element [1] indicates a Y component. An Xcomponent and a Y component of a motion vector difference according toEmbodiment 2 (and Embodiment 1) are combined and described in a stream.Accordingly, a motion vector difference according to Embodiment 2 (andEmbodiment 1) is notated as mvd_I? [x0] [y0].

High-speed coding and high-speed decoding can be achieved by generatingdata having such a structure.

It should be noted that the motion vector difference coding unitaccording to Embodiment 2 is included in the image coding apparatuswhich performs compression coding on image data. FIG. 14 is a blockdiagram showing an example of a configuration of an image codingapparatus 200 according to Embodiment 2.

The image coding apparatus 200 performs compression coding on imagedata. For example, image data is input to the image coding apparatus 200as an input signal for each block. The image coding apparatus 200performs transform, quantization, and variable length coding on theinput signal which has been input, to generate a coded signal.

As shown in FIG. 14, the image coding apparatus 200 includes asubtractor 205, and a transform and quantization unit 210, an entropycoding unit 220, an inverse quantization and inverse transform unit 230,an adder 235, a deblocking filter 240, a memory 250, an intra predictionunit 260, a motion detection unit 270, a motion compensation unit 280,and an intra/inter change switch 290.

The subtractor 205 calculates a difference between an input signal and apredicted signal, or in other words, a prediction error.

The transform and quantization unit 210 transforms a prediction error ina spatial domain to generate a transform coefficient in a frequencydomain. For example, the transform and quantization unit 210 performsdiscrete cosine transform (DCT) on the prediction error, to generate atransform coefficient. Furthermore, the transform and quantization unit210 quantizes the transform coefficient, to generate a quantizationcoefficient.

The entropy coding unit 220 performs variable length coding on thequantization coefficient, to generate a coded signal. Further, theentropy coding unit 220 codes motion data (for example, motion vector)detected by the motion detection unit 270, and outputs the data includedin the coded signal.

The inverse quantization and inverse transform unit 230 performs inversequantization on the quantization coefficient, to reconstruct a transformcoefficient. Furthermore, the inverse quantization and inverse transformunit 230 performs inverse transform on the reconstructed transformcoefficient, to reconstruct the prediction error. It should be notedthat the reconstructed prediction error has information loss due toquantization, and thus does not match the prediction error generated bythe subtractor 205. Specifically, the reconstructed prediction errorincludes a quantization error.

The adder 235 adds the reconstructed prediction error to the predictedsignal, to generate a local decoded image.

The deblocking filter 240 performs deblocking filter processing on thegenerated local decoded image.

The memory 250 is a memory for storing reference images used for motioncompensation. Specifically, the memory 250 stores the locally decodedimage on which deblocking filter processing has been performed.

The intra prediction unit 260 performs intra prediction, to generate apredicted signal (intra-predicted signal). Specifically, the intraprediction unit 260 performs intra prediction by referring to an imagearound a coding target block (input signal) in the locally decoded imagegenerated by the adder 235, to generate an intra-predicted signal.

The motion detection unit 270 detects motion data (for example, motionvector) between an input signal and a reference image stored in thememory 250.

The motion compensation unit 280 performs motion compensation, based onthe detected motion data, to generate a predicted signal(inter-predicted signal).

The intra/inter change switch 290 selects either one of anintra-predicted signal and an inter-predicted signal, and outputs theselected signal as a predicted signal to the subtractor 205 and theadder 235.

Using the above configuration, the image coding apparatus 200 accordingto Embodiment 2 performs compression coding on image data.

Embodiment 3

The present embodiment describes characteristic configurations andprocedures included in Embodiment 1 or 2 for confirmation. Theconfigurations and the procedures according to the present embodimentcorrespond to the configurations and procedures described in Embodiment1 or 2. Specifically, the concept described in Embodiments 1 and 2include the configurations and the procedures according to the presentembodiment.

FIG. 15A is a block diagram showing an example of a configuration of animage coding apparatus according to the present embodiment. An imagecoding apparatus 800 shown in FIG. 15A codes an image using a motionvector. The image coding apparatus 800 includes a coding unit 801.

FIG. 15B is a flowchart showing processing operation of the image codingapparatus 800 shown in FIG. 15A. The coding unit 801 codes a motionvector difference (S801). A motion vector difference shows thedifference between a predicted motion vector and a motion vector. Apredicted motion vector is a predicted value of a motion vector. Whencoding a motion vector difference, the coding unit 801 codes a firstportion, a second portion, a third portion, and a fourth portion.

The first portion is a part of a first component which is one of ahorizontal component and a vertical component of a motion vectordifference. The second portion is a part of a second component which isdifferent from the first component and is the other one of thehorizontal component and the vertical component of the motion vectordifference. The third portion is a part of the first component, and isdifferent from the first portion. The fourth portion is a part of thesecond component, and is different from the second portion. Typically, apart of each component is a part of binary data corresponding to thecomponent.

Then, the coding unit 801 generates a code string which includes thefirst portion, the second portion, the third portion, and the fourthportion in the order of the first portion, the second portion, the thirdportion, and the fourth portion.

Accordingly, a part of the horizontal component of the motion vectordifference and a part of the vertical component of the motion vectordifference are combined in the code string. Thus, the motion vectordifference is efficiently coded by combining a part of the horizontalcomponent and a part of the vertical component.

For example, the first portion may include a flag indicating whether thefirst component is 0. The second portion may include a flag indicatingwhether the second component is 0. The third portion may include thesign of the first component. The fourth portion may include the sign ofthe second component.

Further, for example, if the absolute value of the first component isgreater than a threshold value, the third portion may include thedifference between the threshold value and the absolute value of thefirst component. If the absolute value of the second component isgreater than the threshold value, the fourth portion may include thedifference between the threshold value and the absolute value of thesecond component.

Further, for example, the coding unit 801 may code the first portion andthe second portion by performing context adaptive binary arithmeticcoding. Then, the coding unit 801 may code the third portion and thefourth portion by performing bypass coding. Context adaptive binaryarithmetic coding is arithmetic coding in which a variable probabilityupdated based on coded data is used. Bypass coding is arithmetic codingin which a predetermined fixed probability is used. Further, the codingunit 801 may code the third portion and the fourth portion in parallel.

Further, for example, the coding unit 801 may code the first portion,the second portion, the third portion, and the fourth portion in theorder of the first portion, the second portion, the third portion, andthe fourth portion.

For example, the coding unit 801 may switch coding processing to firstcoding processing conforming to a first standard or to second codingprocessing conforming to a second standard. Then, the coding unit 801may generate a bit stream which includes identification informationindicating the first standard or the second standard to which acorresponding one of the first coding processing and the second codingprocessing to which the coding processing has been switched conforms.

If coding processing is switched to the first coding processing, thecoding unit 801 may generate a code string which includes the firstportion, the second portion, the third portion, and the fourth portionin the order of the first portion, the second portion, the thirdportion, and the fourth portion. In addition, the coding unit 801 maygenerate a bit stream which includes identification informationindicating the first standard and the code string, in this case.

FIG. 16A is a block diagram showing an example of a configuration of animage decoding apparatus according to the present embodiment. An imagedecoding apparatus 900 shown in FIG. 16A decodes an image using a motionvector. Further, the image decoding apparatus 900 includes a decodingunit 901.

FIG. 16B is a flowchart showing processing operation of the imagedecoding apparatus 900 shown in FIG. 16A. The decoding unit 901 decodesa motion vector difference (S901). A predicted motion vector is apredicted value of a motion vector. A motion vector difference shows thedifference between the predicted motion vector and the motion vector.

When decoding a motion vector difference, the decoding unit 901 obtainsa code string. Then, the decoding unit 901 decodes a first portionincluded in the code string, decodes a second portion included in thecode string, decodes a third portion included in the code string, anddecodes a fourth portion included in the code string.

The first portion is a part of a first component which is one of ahorizontal component and a vertical component of a motion vectordifference. The second portion is a part of a second component which isdifferent from the first component and is the other one of thehorizontal component and the vertical component. The third portion is apart of the first component, and is different from the first portion.The fourth portion is a part of the second component, and is differentfrom the second portion. Typically, a part of each component is a partof binary data corresponding to the component.

A code string includes the first portion, the second portion, the thirdportion, and the fourth portion in the order of the first portion, thesecond portion, the third portion, and the fourth portion.

Accordingly, the decoding unit 901 obtains a code string in which a partof the horizontal component of the motion vector difference and a partof the vertical component of the motion vector difference are combined.Then, the motion vector difference is efficiently decoded by using acode string in which a part of the horizontal component and a part ofthe vertical component are combined.

For example, the first portion may include a flag which indicateswhether the first component is 0. The second portion may include a flagwhich indicates whether the second component is 0. The third portion mayinclude the sign of the first component. The fourth portion may includethe sign of the second component.

For example, if the absolute value of the first component is greaterthan a threshold value, the third portion may include the differencebetween the threshold value and the absolute value of the firstcomponent. If the absolute value of the second component is greater thanthe threshold value, the fourth portion may include the differencebetween the threshold value and the absolute value of the secondcomponent.

For example, the decoding unit 901 may decode the first portion and thesecond portion by performing context adaptive binary arithmeticdecoding. Further, the decoding unit 901 may decode the third portionand the fourth portion by performing bypass decoding. Context adaptivebinary arithmetic decoding is arithmetic decoding in which a variableprobability updated based on decoded data is used. Bypass decoding isarithmetic decoding in which a predetermined fixed probability is used.In addition, the decoding unit 901 may decode the third portion and thefourth portion in parallel.

For example, the decoding unit 901 may decode the first portion, thesecond portion, the third portion, and the fourth portion in the orderof the first portion, the second portion, the third portion, and thefourth portion.

Further, for example, the decoding unit 901 may obtain a bit streamwhich includes identification information indicating a first standard ora second standard. Then, based on the identification information, thedecoding unit 901 may switch decoding processing to first decodingprocessing conforming to the first standard or to second decodingprocessing conforming to the second standard.

If decoding processing is switched to the first decoding processing, thedecoding unit 901 may obtain, from the bit stream, the code string whichincludes the first portion, the second portion, the third portion, andthe fourth portion in the order of the first portion, the secondportion, the third portion, and the fourth portion.

Further, for example, the image coding apparatus 800 and the imagedecoding apparatus 900 may constitute an image coding and decodingapparatus.

Further, for example, the data structure corresponding to a code stringof a motion vector difference may be the data structure shown in FIG.17.

FIG. 17 shows a syntax table showing an example of a data structurecorresponding to a code string of a motion vector difference. In FIG.17, [0] indicates a horizontal component, whereas [1] indicates avertical component.

“abs_mvd_greater0_flag” is a flag which indicates whether the absolutevalue of a horizontal component or a vertical component of a motionvector difference is greater than 0. “abs_mvd_greater1_flag” is a flagwhich indicates whether the absolute value of the horizontal componentor the vertical component of the motion vector difference is greaterthan 1. “abs_mvd_minus2” is a value obtained by subtracting 2 from theabsolute value of the horizontal component or the vertical component ofthe motion vector difference. “mvd_sign_flag” is a sign of thehorizontal component or the vertical component of the motion vectordifference.

“abs_mvd_greater0_flag” and “abs_mvd_greater1_flag” correspond to aprefix portion. “abs_mvd_minus2” corresponds to a suffix portion.Typically, context adaptive binary arithmetic coding (decoding) is usedfor coding (decoding) “abs_mvd_greater0_flag” and“abs_mvd_greater1_flag”. Then, bypass coding (decoding) is used forcoding (decoding) “abs_mvd_minus2” and “mvd_sign_flag”.

It should be noted that in the above embodiments, each of theconstituent elements may be constituted by dedicated hardware, or may beobtained by executing a software program suitable for the constituentelement. Each constituent element may be obtained by a program executionunit such as a CPU or a processor reading and executing a softwareprogram recorded on a recording medium such as a hard disk orsemiconductor memory. Here, the software which realizes the image codingapparatus in the above embodiments and the like is a program as will bedescribed below.

Specifically, this program causes a computer to execute an image codingmethod for coding an image using a motion vector, the method includingcoding a motion vector difference indicating a difference between themotion vector and a predicted motion vector which is a predicted valueof the motion vector, wherein the coding includes: coding a firstportion that is a part of a first component which is one of a horizontalcomponent and a vertical component of the motion vector difference;coding a second portion that is a part of a second component which isdifferent from the first component and is the other one of thehorizontal component and the vertical component; coding a third portionthat is a part of the first component and is different from the firstportion; coding a fourth portion that is a part of the second componentand is different from the second portion; and generating a code stringwhich includes the first portion, the second portion, the third portion,and the fourth portion in an order of the first portion, the secondportion, the third portion, and the fourth portion.

The above is a description of an image coding method according to one ormore aspects of the inventive concept, the scope of which is defined inthe appended Claims and their equivalents, based on some exemplaryembodiments. However, the inventive concept is not limited to theseexemplary embodiments. Those skilled in the art will readily appreciatethat it is possible to make various modifications in these exemplaryembodiments and to arbitrarily combine the constituent elements in theexemplary embodiments without materially departing from the principlesand spirit of the inventive concept.

Embodiment 4

The processing described in each of embodiments can be simplyimplemented in an independent computer system, by recording, in arecording medium, a program for implementing the configurations of themoving picture coding method (image coding method) and the movingpicture decoding method (image decoding method) described in each ofembodiments. The recording media may be any recording media as long asthe program can be recorded, such as a magnetic disk, an optical disk, amagnetic optical disk, an IC card, and a semiconductor memory.

Hereinafter, the applications to the moving picture coding method (imagecoding method) and the moving picture decoding method (image decodingmethod) described in each of embodiments and systems using thereof willbe described. The system has a feature of having an image coding anddecoding apparatus that includes an image coding apparatus using theimage coding method and an image decoding apparatus using the imagedecoding method. Other configurations in the system can be changed asappropriate depending on the cases.

FIG. 18 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106, ex107, ex108, ex109, and ex110 which arefixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 18, and a combination inwhich any of the elements are connected is acceptable. In addition, eachdevice may be directly connected to the telephone network ex104, ratherthan via the base stations ex106 to ex110 which are the fixed wirelessstations. Furthermore, the devices may be interconnected to each othervia a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital video camera, iscapable of capturing both still images and video. Furthermore, thecellular phone ex114 may be the one that meets any of the standards suchas Global System for Mobile Communications (GSM) (registered trademark),Code Division Multiple Access (CDMA), Wideband-Code Division MultipleAccess (W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of images of alive show and others. In such a distribution, a content (for example,video of a music live show) captured by the user using the camera ex113is coded as described above in each of embodiments (i.e., the camerafunctions as the image coding apparatus according to an aspect of thepresent disclosure), and the coded content is transmitted to thestreaming server ex103. On the other hand, the streaming server ex103carries out stream distribution of the transmitted content data to theclients upon their requests. The clients include the computer ex111, thePDA ex112, the camera ex113, the cellular phone ex114, and the gamemachine ex115 that are capable of decoding the above-mentioned codeddata. Each of the devices that have received the distributed datadecodes and reproduces the coded data (i.e., functions as the imagedecoding apparatus according to an aspect of the present disclosure).

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding and decoding processes may be performed by anLSI ex500 generally included in each of the computer ex111 and thedevices. The LSI ex500 may be configured of a single chip or a pluralityof chips. Software for coding and decoding video may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, anda hard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.Furthermore, when the cellular phone ex114 is equipped with a camera,the image data obtained by the camera may be transmitted. The video datais data coded by the LSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients may receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the moving picture coding apparatus (image coding apparatus) andthe moving picture decoding apparatus (image decoding apparatus)described in each of embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 19. More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data coded bythe moving picture coding method described in each of embodiments (i.e.,data coded by the image coding apparatus according to an aspect of thepresent disclosure). Upon receipt of the multiplexed data, the broadcastsatellite ex202 transmits radio waves for broadcasting. Then, a home-useantenna ex204 with a satellite broadcast reception function receives theradio waves. Next, a device such as a television (receiver) ex300 and aset top box (STB) ex217 decodes the received multiplexed data, andreproduces the decoded data (i.e., functions as the image decodingapparatus according to an aspect of the present disclosure).

Furthermore, a reader/recorder ex218 (i) reads and decodes themultiplexed data recorded on a recording media ex215, such as a DVD anda BD, or (i) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data. The reader/recorder ex218 can include the moving picturedecoding apparatus or the moving picture coding apparatus as shown ineach of embodiments. In this case, the reproduced video signals aredisplayed on the monitor ex219, and can be reproduced by another deviceor system using the recording medium ex215 on which the multiplexed datais recorded. It is also possible to implement the moving picturedecoding apparatus in the set top box ex217 connected to the cable ex203for a cable television or to the antenna ex204 for satellite and/orterrestrial broadcasting, so as to display the video signals on themonitor ex219 of the television ex300. The moving picture decodingapparatus may be implemented not in the set top box but in thetelevision ex300.

FIG. 20 illustrates the television (receiver) ex300 that uses the movingpicture coding method and the moving picture decoding method describedin each of embodiments. The television ex300 includes: a tuner ex301that obtains or provides multiplexed data obtained by multiplexing audiodata onto video data, through the antenna ex204 or the cable ex203, etc.that receives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 that decode audio data and video data and codeaudio data and video data, respectively (which function as the imagecoding apparatus and the image decoding apparatus according to theaspects of the present disclosure); and an output unit ex309 including aspeaker ex307 that provides the decoded audio signal, and a display unitex308 that displays the decoded video signal, such as a display.Furthermore, the television ex300 includes an interface unit ex317including an operation input unit ex312 that receives an input of a useroperation. Furthermore, the television ex300 includes a control unitex310 that controls overall each constituent element of the televisionex300, and a power supply circuit unit ex311 that supplies power to eachof the elements. Other than the operation input unit ex312, theinterface unit ex317 may include: a bridge ex313 that is connected to anexternal device, such as the reader/recorder ex218; a slot unit ex314for enabling attachment of the recording medium ex216, such as an SDcard; a driver ex315 to be connected to an external recording medium,such as a hard disk; and a modem ex316 to be connected to a telephonenetwork. Here, the recording medium ex216 can electrically recordinformation using a non-volatile/volatile semiconductor memory elementfor storage. The constituent elements of the television ex300 areconnected to each other through a synchronous bus.

First, the configuration in which the television ex300 decodesmultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon a user operation through a remote controllerex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside, respectively. When the output unit ex309 provides thevideo signal and the audio signal, the signals may be temporarily storedin buffers ex318 and ex319, and others so that the signals arereproduced in synchronization with each other. Furthermore, thetelevision ex300 may read multiplexed data not through a broadcast andothers but from the recording media ex215 and ex216, such as a magneticdisk, an optical disk, and a SD card. Next, a configuration in which thetelevision ex300 codes an audio signal and a video signal, and transmitsthe data outside or writes the data on a recording medium will bedescribed. In the television ex300, upon a user operation through theremote controller ex220 and others, the audio signal processing unitex304 codes an audio signal, and the video signal processing unit ex305codes a video signal, under control of the control unit ex310 using thecoding method described in each of embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in thebuffers ex320 and ex321, and others so that the signals are reproducedin synchronization with each other. Here, the buffers ex318, ex319,ex320, and ex321 may be plural as illustrated, or at least one buffermay be shared in the television ex300. Furthermore, data may be storedin a buffer so that the system overflow and underflow may be avoidedbetween the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be capable of only receiving, decoding, andproviding outside data but not the coding, multiplexing, and providingoutside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may decode or code the multiplexed data, and thetelevision ex300 and the reader/recorder ex218 may share the decoding orcoding.

As an example, FIG. 21 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or onan optical disk. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot in a recording surface of the recording medium ex215 thatis an optical disk to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. The disk motor ex405 rotates therecording medium ex215. The servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 22 illustrates the recording medium ex215 that is the optical disk.On the recording surface of the recording medium ex215, guide groovesare spirally formed, and an information track ex230 records, in advance,address information indicating an absolute position on the diskaccording to change in a shape of the guide grooves. The addressinformation includes information for determining positions of recordingblocks ex231 that are a unit for recording data. Reproducing theinformation track ex230 and reading the address information in anapparatus that records and reproduces data can lead to determination ofthe positions of the recording blocks. Furthermore, the recording mediumex215 includes a data recording area ex233, an inner circumference areaex232, and an outer circumference area ex234. The data recording areaex233 is an area for use in recording the user data. The innercircumference area ex232 and the outer circumference area ex234 that areinside and outside of the data recording area ex233, respectively arefor specific use except for recording the user data. The informationreproducing/recording unit 400 reads and writes coded audio, coded videodata, or multiplexed data obtained by multiplexing the coded audio andvideo data, from and on the data recording area ex233 of the recordingmedium ex215.

Although an optical disk having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disk is notlimited to such, and may be an optical disk having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disk may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disk and for recording information havingdifferent layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be a configuration, for example, includinga GPS receiving unit from the configuration illustrated in FIG. 20. Thesame will be true for the configuration of the computer ex111, thecellular phone ex114, and others.

FIG. 23A illustrates the cellular phone ex114 that uses the movingpicture coding method and the moving picture decoding method describedin embodiments. The cellular phone ex114 includes: an antenna ex350 fortransmitting and receiving radio waves through the base station ex110; acamera unit ex365 capable of capturing moving and still images; and adisplay unit ex358 such as a liquid crystal display for displaying thedata such as decoded video captured by the camera unit ex365 or receivedby the antenna ex350. The cellular phone ex114 further includes: a mainbody unit including an operation key unit ex366; an audio output unitex357 such as a speaker for output of audio; an audio input unit ex356such as a microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still pictures, e-mails, or others; and aslot unit ex364 that is an interface unit for a recording medium thatstores data in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 23B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keyunit ex366 is connected mutually, via a synchronous bus ex370, to apower supply circuit unit ex361, an operation input control unit ex362,a video signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex357.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation key unitex366 and others of the main body is sent out to the main control unitex360 via the operation input control unit ex362. The main control unitex360 causes the modulation/demodulation unit ex352 to perform spreadspectrum processing on the text data, and the transmitting and receivingunit ex351 performs the digital-to-analog conversion and the frequencyconversion on the resulting data to transmit the data to the basestation ex110 via the antenna ex350. When an e-mail is received,processing that is approximately inverse to the processing fortransmitting an e-mail is performed on the received data, and theresulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving picture coding method shown in each of embodiments (i.e.,functions as the image coding apparatus according to the aspect of thepresent disclosure), and transmits the coded video data to themultiplexing/demultiplexing unit ex353. In contrast, during when thecamera unit ex365 captures video, still images, and others, the audiosignal processing unit ex354 codes audio signals collected by the audioinput unit ex356, and transmits the coded audio data to themultiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the multiplexed data, and the transmitting and receivingunit ex351 performs digital-to-analog conversion and frequencyconversion on the data so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bit stream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using amoving picture decoding method corresponding to the moving picturecoding method shown in each of embodiments (i.e., functions as the imagedecoding apparatus according to the aspect of the present disclosure),and then the display unit ex358 displays, for instance, the video andstill images included in the video file linked to the Web page via theLCD control unit ex359. Furthermore, the audio signal processing unitex354 decodes the audio signal, and the audio output unit ex357 providesthe audio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 probably have 3 types of implementationconfigurations including not only (i) a transmitting and receivingterminal including both a coding apparatus and a decoding apparatus, butalso (ii) a transmitting terminal including only a coding apparatus and(iii) a receiving terminal including only a decoding apparatus. Althoughthe digital broadcasting system ex200 receives and transmits themultiplexed data obtained by multiplexing audio data onto video data inthe description, the multiplexed data may be data obtained bymultiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving picture coding method and the moving picturedecoding method in each of embodiments can be used in any of the devicesand systems described. Thus, the advantages described in each ofembodiments can be obtained.

Furthermore, the present disclosure is not limited to embodiments, andvarious modifications and revisions are possible without departing fromthe scope of the present disclosure.

Embodiment 5

Video data can be generated by switching, as necessary, between (i) themoving picture coding method or the moving picture coding apparatusshown in each of embodiments and (ii) a moving picture coding method ora moving picture coding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconform cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture coding method and by themoving picture coding apparatus shown in each of embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG-2 Transport Stream format.

FIG. 24 illustrates a structure of the multiplexed data. As illustratedin FIG. 24, the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of the movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the primary video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is coded in the moving picture coding method or by themoving picture coding apparatus shown in each of embodiments, or in amoving picture coding method or by a moving picture coding apparatus inconformity with a conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1. The audio stream is coded in accordance with a standard, such asDolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary video to be mixed with the primary audio.

FIG. 25 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 26 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 26 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 26, the video stream is divided into pictures as I pictures, Bpictures, and P pictures each of which is a video presentation unit, andthe pictures are stored in a payload of each of the PES packets. Each ofthe PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 27 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The source packets are arranged in the multiplexed dataas shown at the bottom of FIG. 27. The numbers incrementing from thehead of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 28 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 29. The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 29, the multiplexed data includes a system rate,a reproduction start time, and a reproduction end time. The system rateindicates the maximum transfer rate at which a system target decoder tobe described later transfers the multiplexed data to a PID filter. Theintervals of the ATSs included in the multiplexed data are set to nothigher than a system rate. The reproduction start time indicates a PTSin a video frame at the head of the multiplexed data. An interval of oneframe is added to a PTS in a video frame at the end of the multiplexeddata, and the PTS is set to the reproduction end time.

As shown in FIG. 30, a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In the present embodiment, the multiplexed data to be used is of astream type included in the PMT. Furthermore, when the multiplexed datais recorded on a recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, the moving picture coding method or the moving picturecoding apparatus described in each of embodiments includes a step or aunit for allocating unique information indicating video data generatedby the moving picture coding method or the moving picture codingapparatus in each of embodiments, to the stream type included in the PMTor the video stream attribute information. With the configuration, thevideo data generated by the moving picture coding method or the movingpicture coding apparatus described in each of embodiments can bedistinguished from video data that conforms to another standard.

Furthermore, FIG. 31 illustrates steps of the moving picture decodingmethod according to the present embodiment. In Step exS100, the streamtype included in the PMT or the video stream attribute information isobtained from the multiplexed data. Next, in Step exS101, it isdetermined whether or not the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving picture coding method or the moving picture coding apparatus ineach of embodiments. When it is determined that the stream type or thevideo stream attribute information indicates that the multiplexed datais generated by the moving picture coding method or the moving picturecoding apparatus in each of embodiments, in Step exS102, decoding isperformed by the moving picture decoding method in each of embodiments.Furthermore, when the stream type or the video stream attributeinformation indicates conformance to the conventional standards, such asMPEG-2, MPEG-4 AVC, and VC-1, in Step exS103, decoding is performed by amoving picture decoding method in conformity with the conventionalstandards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving picture decoding method or the moving picture decoding apparatusthat is described in each of embodiments can perform decoding. Even whenmultiplexed data that conforms to a different standard, an appropriatedecoding method or apparatus can be selected. Thus, it becomes possibleto decode information without any error. Furthermore, the moving picturecoding method or apparatus, or the moving picture decoding method orapparatus in the present embodiment can be used in the devices andsystems described above.

Embodiment 6

Each of the moving picture coding method, the moving picture codingapparatus, the moving picture decoding method, and the moving picturedecoding apparatus in each of embodiments is typically achieved in theform of an integrated circuit or a Large Scale Integrated (LSI) circuit.As an example of the LSI, FIG. 32 illustrates a configuration of the LSIex500 that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AVIO ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recording mediaex215. When data sets are multiplexed, the data should be temporarilystored in the buffer ex508 so that the data sets are synchronized witheach other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the inventive conceptis applied to biotechnology.

Embodiment 7

When video data generated in the moving picture coding method or by themoving picture coding apparatus described in each of embodiments isdecoded, compared to when video data that conforms to a conventionalstandard, such as MPEG-2, MPEG-4 AVC, and VC-1 is decoded, theprocessing amount probably increases. Thus, the LSI ex500 needs to beset to a driving frequency higher than that of the CPU ex502 to be usedwhen video data in conformity with the conventional standard is decoded.However, when the driving frequency is set higher, there is a problemthat the power consumption increases.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 33illustrates a configuration ex800 in the present embodiment. A drivingfrequency switching unit ex803 sets a driving frequency to a higherdriving frequency when video data is generated by the moving picturecoding method or the moving picture coding apparatus described in eachof embodiments. Then, the driving frequency switching unit ex803instructs a decoding processing unit ex801 that executes the movingpicture decoding method described in each of embodiments to decode thevideo data. When the video data conforms to the conventional standard,the driving frequency switching unit ex803 sets a driving frequency to alower driving frequency than that of the video data generated by themoving picture coding method or the moving picture coding apparatusdescribed in each of embodiments. Then, the driving frequency switchingunit ex803 instructs the decoding processing unit ex802 that conforms tothe conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 32.Here, each of the decoding processing unit ex801 that executes themoving picture decoding method described in each of embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 32. TheCPU ex502 determines to which standard the video data conforms. Then,the driving frequency control unit ex512 determines a driving frequencybased on a signal from the CPU ex502. Furthermore, the signal processingunit ex507 decodes the video data based on the signal from the CPUex502. For example, the identification information described inEmbodiment 5 is probably used for identifying the video data. Theidentification information is not limited to the one described inEmbodiment 5 but may be any information as long as the informationindicates to which standard the video data conforms. For example, whenwhich standard video data conforms to can be determined based on anexternal signal for determining that the video data is used for atelevision or a disk, etc., the determination may be made based on suchan external signal. Furthermore, the CPU ex502 selects a drivingfrequency based on, for example, a look-up table in which the standardsof the video data are associated with the driving frequencies as shownin FIG. 35. The driving frequency can be selected by storing the look-uptable in the buffer ex508 and in an internal memory of an LSI, and withreference to the look-up table by the CPU ex502.

FIG. 34 illustrates steps for executing a method in the presentembodiment. First, in Step exS200, the signal processing unit ex507obtains identification information from the multiplexed data. Next, inStep exS201, the CPU ex502 determines whether or not the video data isgenerated by the coding method and the coding apparatus described ineach of embodiments, based on the identification information. When thevideo data is generated by the moving picture coding method and themoving picture coding apparatus described in each of embodiments, inStep exS202, the CPU ex502 transmits a signal for setting the drivingfrequency to a higher driving frequency to the driving frequency controlunit ex512. Then, the driving frequency control unit ex512 sets thedriving frequency to the higher driving frequency. On the other hand,when the identification information indicates that the video dataconforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1, in Step exS203, the CPU ex502 transmits a signal for setting thedriving frequency to a lower driving frequency to the driving frequencycontrol unit ex512. Then, the driving frequency control unit ex512 setsthe driving frequency to the lower driving frequency than that in thecase where the video data is generated by the moving picture codingmethod and the moving picture coding apparatus described in each ofembodiment.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the processing amount for decoding is larger, thedriving frequency may be set higher, and when the processing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when theprocessing amount for decoding video data in conformity with MPEG-4 AVCis larger than the processing amount for decoding video data generatedby the moving picture coding method and the moving picture codingapparatus described in each of embodiments, the driving frequency isprobably set in reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture coding method and the moving picturecoding apparatus described in each of embodiments, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set higher. When the identification information indicates thatthe video data conforms to the conventional standard, such as MPEG-2,MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or theapparatus including the LSI ex500 is probably set lower. As anotherexample, when the identification information indicates that the videodata is generated by the moving picture coding method and the movingpicture coding apparatus described in each of embodiments, the drivingof the CPU ex502 does not probably have to be suspended. When theidentification information indicates that the video data conforms to theconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the drivingof the CPU ex502 is probably suspended at a given time because the CPUex502 has extra processing capacity. Even when the identificationinformation indicates that the video data is generated by the movingpicture coding method and the moving picture coding apparatus describedin each of embodiments, in the case where the CPU ex502 has extraprocessing capacity, the driving of the CPU ex502 is probably suspendedat a given time. In such a case, the suspending time is probably setshorter than that in the case where when the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Embodiment 8

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a mobile phone. In order to enable decoding the pluralityof video data that conforms to the different standards, the signalprocessing unit ex507 of the LSI ex500 needs to conform to the differentstandards. However, the problems of increase in the scale of the circuitof the LSI ex500 and increase in the cost arise with the individual useof the signal processing units ex507 that conform to the respectivestandards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 36A showsan example of the configuration. For example, the moving picturedecoding method described in each of embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy coding, inverse quantization,deblocking filtering, and motion compensated prediction. The details ofprocessing to be shared probably include use of a decoding processingunit ex902 that conforms to MPEG-4 AVC. In contrast, a dedicateddecoding processing unit ex901 is probably used for other processingunique to an aspect of the present disclosure. Since the aspect of thepresent disclosure is characterized by entropy decoding in particular,for example, the dedicated decoding processing unit ex901 is used forentropy decoding. Otherwise, the decoding processing unit is probablyshared for one of inverse quantization, deblocking filtering, and motioncompensation, or all of the processing. The decoding processing unit forimplementing the moving picture decoding method described in each ofembodiments may be shared for the processing to be shared, and adedicated decoding processing unit may be used for processing unique tothat of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 36B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to an aspect of the present disclosure, a dedicated decodingprocessing unit ex1002 that supports the processing unique to anotherconventional standard, and a decoding processing unit ex1003 thatsupports processing to be shared between the moving picture decodingmethod according to the aspect of the present disclosure and theconventional moving picture decoding method. Here, the dedicateddecoding processing units ex1001 and ex1002 are not necessarilyspecialized for the processing according to the aspect of the presentdisclosure and the processing of the conventional standard,respectively, and may be the ones capable of implementing generalprocessing. Furthermore, the configuration of the present embodiment canbe implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving picture decoding methodaccording to the aspect of the present disclosure and the moving picturedecoding method in conformity with the conventional standard.

INDUSTRIAL APPLICABILITY

The image coding method and the image decoding method according to anaspect of the present disclosure is applicable to, for example,television receivers, digital video recorders, car navigation systems,cellular phones, digital cameras, and digital video cameras.

The invention claimed is:
 1. A providing method comprising: transmittinga bitstream from a server to a terminal in response to an instructionfrom the terminal, the bitstream including an encoded image on which anencoding process has been performed, wherein the encoding processincludes: deriving a difference motion vector indicating a differencebetween a motion vector used to predict the image and a motion vectorpredictor that is a prediction of the motion vector; binarizing thedifference motion vector into first binary data and second binary data,the first binary data indicating a horizontal component of thedifference motion vector and the second binary data indicating avertical component of the difference motion vector; encoding a firstflag, a second flag, a first prefix, a second prefix, a first suffix,and a second suffix respectively into an encoded first flag, an encodedsecond flag, an encoded first prefix, an encoded second prefix, anencoded first suffix, and an encoded second suffix, the first binarydata including (i) the first flag which indicates whether or not thehorizontal component is 0 and which is to be encoded by performingcontext adaptive binary arithmetic coding in which a variableprobability is used, (ii) the first prefix which is to be encoded byperforming the context adaptive binary arithmetic coding and which isdifferent from the first flag, and (iii) the first suffix which is to beencoded by performing bypass coding in which a fixed probability isused, and the second binary data including (i) the second flag whichindicates whether or not the vertical component is 0 and which is to beencoded by performing the context adaptive binary arithmetic coding,(ii) the second prefix which is to be encoded by performing the contextadaptive binary arithmetic coding and which is different from the secondflag, and (iii) the second suffix which is to be encoded by performingthe bypass coding; and arranging the encoded first flag, the encodedsecond flag, the encoded first prefix, the encoded second prefix, theencoded first suffix, and the encoded second suffix in the bitstream, inthis order.
 2. A method for managing content in a communication system,the method comprising: receiving a bitstream generated by encoding animage using an encoding method, from a first terminal; storing thebitstream at a server; receiving a request for providing the bitstreamfrom a second terminal; and providing the bitstream from the server tothe second terminal in response to the request, wherein the encodingmethod includes: deriving a difference motion vector indicating adifference between a motion vector used to predict the image and amotion vector predictor that is a prediction of the motion vector;binarizing the difference motion vector into first binary data andsecond binary data, the first binary data indicating a horizontalcomponent of the difference motion vector and the second binary dataindicating a vertical component of the difference motion vector;encoding a first flag, a second flag, a first prefix, a second prefix, afirst suffix, and a second suffix respectively into an encoded firstflag, an encoded second flag, an encoded first prefix, an encoded secondprefix, an encoded first suffix, and an encoded second suffix, the firstbinary data including (i) the first flag which indicates whether or notthe horizontal component is 0 and which is to be encoded by performingcontext adaptive binary arithmetic coding in which a variableprobability is used, (ii) the first prefix which is to be encoded byperforming the context adaptive binary arithmetic coding and which isdifferent from the first flag, and (iii) the first suffix which is to beencoded by performing bypass coding in which a fixed probability isused, and the second binary data including (i) the second flag whichindicates whether or not the vertical component is 0 and which is to beencoded by performing the context adaptive binary arithmetic coding,(ii) the second prefix which is to be encoded by performing the contextadaptive binary arithmetic coding and which is different from the secondflag, and (iii) the second suffix which is to be encoded by performingthe bypass coding; and arranging the encoded first flag, the encodedsecond flag, the encoded first prefix, the encoded second prefix, theencoded first suffix, and the encoded second suffix in the bitstream, inthis order.
 3. A communication system comprising: a server in whichimage data are stored; and a communication apparatus, wherein the imagedata includes a first bitstream and a second bitstream, the firstbitstream being generated by encoding an image using a first encodingmethod and the second bitstream being generated by encoding the imageusing a second encoding method different from the first encoding method,wherein the communication apparatus includes: a receiver configured toreceive a request for providing the image from a terminal; and atransmitter configured to transmit at least one of the first bitstreamand the second bitstream from the server to the terminal, in response tothe request, and wherein the first encoding method comprises: deriving adifference motion vector indicating a difference between a motion vectorused to predict the image and a motion vector predictor that is aprediction of the motion vector; binarizing the difference motion vectorinto first binary data and second binary data, the first binary dataindicating a horizontal component of the difference motion vector andthe second binary data indicating a vertical component of the differencemotion vector; encoding the first binary data and the second binary datainto encoded first binary data and encoded second binary data; andarranging the encoded first binary data and the encoded second binarydata in the first bitstream, in this order, and wherein the secondencoding method comprises: deriving a difference motion vectorindicating a difference between a motion vector used to predict theimage and a motion vector predictor that is a prediction of the motionvector; binarizing the difference motion vector into first binary dataand second binary data, the first binary data indicating a horizontalcomponent of the difference motion vector and the second binary dataindicating a vertical component of the difference motion vector;encoding a first flag, a second flag, a first prefix, a second prefix, afirst suffix, and a second suffix respectively into an encoded firstflag, an encoded second flag, an encoded first prefix, an encoded secondprefix, an encoded first suffix, and an encoded second suffix, the firstbinary data including (i) the first flag which indicates whether or notthe horizontal component is 0 and which is to be encoded by performingcontext adaptive binary arithmetic coding in which a variableprobability is used, (ii) the first prefix which is to be encoded byperforming the context adaptive binary arithmetic coding and which isdifferent from the first flag, and (iii) the first suffix which is to beencoded by performing bypass coding in which a fixed probability isused, and the second binary data including (i) the second flag whichindicates whether or not the vertical component is 0 and which is to beencoded by performing the context adaptive binary arithmetic coding,(ii) the second prefix which is to be encoded by performing the contextadaptive binary arithmetic coding and which is different from the secondflag, and (iii) the second suffix which is to be encoded by performingthe bypass coding; and arranging the encoded first flag, the encodedsecond flag, the encoded first prefix, the encoded second prefix, theencoded first suffix, and the encoded second suffix in the bitstream, inthis order.